Detonating fuse

ABSTRACT

Detonating fuse having a core of high explosive and being enclosed by a casing or sheath, wherein at least one hollow space is arranged within the explosive core. The hollow space extends over the entire length and is provided with a lining surrounding this hollow space with respect to the explosive surrounding the same on all sides.

United States Patent n91 Prior 51 Ma 1 1973 s41 DETONATING F 3,253,333 2x332 grandy at al. ..10;/27 R ..10 27 R [75] Inventor: Josef Prior, Troisdorf, Germany ersson I [73] Assignee: Dynamit Nobel Aktiengesellschaft, Primary Pendegras? Troisdorf Germany AttorneyCra1g, Antonelh, Stewart & HI"

[22] Filed: Dec. 1, 1970 21 Appl. No.: 94,086 [57] ABSTRACT Detonating fuse having a core of high explosive and being enclosed by a casing or sheath, wherein at least [52] :U.S.Cl... v ..l02/27R hollow Space is arranged within the explosive core; The hollow space extends over the entire g h [58] Fleld of Search ..l02/27 R and is provided i a li i Surrounding this hollow space with respect to the explosive surrounding the [56] References Cited same on all sides.

UNITED STATES PATENTS 16 Claims, 1 Drawing Figure 2,982,210 5/1961 Andrew at al. ..|o2/27 R Patented May 1, 1973 3,730,096

INVENTOR JOSEF PRIOR ATTORNEYS DETONATING FUSE BACKGROUND OF THE INVENTION The present invention relates to a detonating fuse having a core of high explosive and being enclosed by a sheath or casing.

Fuses are employed for transmitting the detonation of a blasting cap or an explosive charge to a second explosive charge at any desired distance. These fuses consist of an explosive core which, in most cases, is either provided with a wound envelope of filaments or strips of any desired material or embedded in a casing of a ductile metal or a thermoplastic material.

An essential feature for the ability of such fuses to transmit the detonation also to those explosive charges which are ignitable only with difficulty is the detonation velocity thereof, in addition to the gross weight indicating the amount of explosive per meter. The gross weight can vary, depending on the purpose of use, from several tenths of a gram up to several decagrams per meter.

The detonation velocity, in turn, is dependent on the charge density, i.e., on the proportion of the diameter of the explosive core to the amount of explosive contained therein. A high charge density in fuses is obtained, for example, by compressing the powdery explosive to the desired diameter of the explosive core after introduction into a sheath. By means of this method, a sufficient amount of densification is still attained for fuses having a gross charge weight of up to about 20 grams per meter. in case of higher gross weights, i.e., in case of a larger diameter of the explosive core, the compressive force exerted on the particles of explosive in the radial direction will not be propagated any more in an unlimited manner, so that, with an increase in the diameter, a lesser amount of compression and thus a lower charge density result. However, this means simultaneously a reduction of the detonation velocity.

SUMMARY OF THE INVENTION The present invention aims at overcoming the problem of increasing the detonation velocityof ain detonation fuses can stem from various reasons. It is important to increase the detonation velocity, especially in case of fuses having an especially high gross weight (35 grams per meter and more), since fuses with such gross weights have inherently lower detonation velocities.

It is further advantageous to provide blasting or explosive systems with an initiation of the detonation at an extremely high velocity, so that a safe and effective blasting method is achieved in the transmission of the detonation to branches or to explosive charges having low detonation velocities.

The present invention provides a detonation fuse wherein at least one hollow space is arranged within the explosive core, which hollow space extends over the entire length and is provided with a lining separating this hollow space with respect to the explosive surrounding the same on all sides. The detonation fuse designed in accordance with the present invention has a substantially higher detonation velocity as compared to a comparable fuse without a hollow space. In all cases wherein heretofore the detonation velocity of a fuse was relatively low or where there was even the danger of an arrest of the detonation, the device of the present invention can be employed to overcome this disadvantage. By provision of this hollow space within the explosive core, the detonation velocity of an explosive having a degree of compression which normally permits only a low detonation velocity is considerably increased and thus a safe functioning is made possible even in critical density ranges. This also holds true for explosives having a large reaction zone length which is, for example, substantially larger than that of hexogen or cyclotetramethylenetetramine, which explosives can only be employed as a fuse core if the explosive core diameter is selected to be sufficiently large. For these explosives, the present invention eliminates the danger of too low a detonation velocity due to an insufficient or compression densification of the explosive.

The hollow space provided in accordance with the present invention is suitably arranged centrally within the explosive core. This results in an optimum increase .in detonation velocity. The hollow space extending along the entire axial length of the fuse is formed, according to a further feature of the present invention, with a constant cross section, preferably with a circular cross section. However, other geometric shapes are likewise possible such as, for example, an equilateral triangle.

An important factor for the attainable increase in the detonation velocity of a fuse according to the present invention is the choice of material for the lining of the hollow space. According to a further aspect of the present invention, the lining is made from a firm but pliable material such as, for example, a thermoplastic synthetic resin, wherein polyolef'ms, such as high-pressure polyethylene and polypropylene are particularly suitable. With such a pliable material, sufficient resistance of the lining with respect to the pressure of the surrounding fuse is ensured, on the one hand, so that the cavity is not narrowed by such pressure and, on the other hand, the flexibility of the fuse is retained. However, in place of the thermoplastic synthetic material, it is also possible to employ a suitable ductile metal, e.g. copper, for the lining. The lining, however, should always have a structure which is as homogenous as possible. Especially suitable prove to be flexible hoses or tubes which are embedded in the explosive. In this connection, it is also within the scope of the present invention to provide more than one hose such as, for example, three hoses centrally within the explosive core.

in addition to the material of the lining for the cavity within the explosive core, other aspects governing for the attainable increase in detonation velocity are the ratio of the size of the cavity with respect to the diameter of the explosive core, as well as the wall thickness of the lining. Especially with respect to the wall thickness, it has been found that the increase in detonation velocity is. again reduced in case of too large a wall thickness depending on the material employed.

BRIEF DESCRIPTICN OF THE DRAWING from the following description when taken in conjunction with the accompanying drawing which shows, for purposes of illustration only, an embodiment in accordance with the present invention and wherein:

The sole FIGURE is a cross-sectional view of the detonation fuse in accordance with the present invennon.

DETAILED DESCRIPTION OF THE DRAWING Referring now to the sole FIGURE, the explosive core 3 is made of, for example, hexogen, normally granulated or very finely granulated penthrite, or hexanitro-oxanilide or other secondary explosives and is provided with a spun sheath or casing 4 of several layers of filaments of a synthetic resin and/or natrual fibers. The sheath 4 is covered on the outside with the waterproof thermoplastic coating 5. The hollow space 1 is arranged centrally within the explosive core 3 and is separated from the explosive by means of the lining 2. Increases in the detonation velocity attained by means of the present invention can be derived from the following three examples.

EXAMPLE 1 Fuse filling penthrite Quantity 12 g. /m. Diameter of fuse 5.0 mm. Detonation velocity: a. Without cavity 7100 m. lsec.

b. Hose insert Polyethylene, 2 mm. diameter, inside diameter 1 mm. 7600 m. lsec.

EXAMPLE II Fuse filling penthrite Quantity 40 g. lm. Diameter of fuse 12 mm. Detonation velocity: a. Without cavity 5800 m. lsec. b. Hose insert Polyethylene, 3 mm. diameter, inside diameter 1 mm. 8300 m. lsec.

EXAMPLE III Fuse filling hexanitro-oxanilide Quantity 15 3. lm. Diameter of fuse 5.5 mm. Detonation velocity: :1. Without cavity 4800 m. lsec.

b. With hose insert Polypropylene, 2 mm. diameter, inside diameter 1 mm.

by the scope of the present invention. Therefore, I do not wish to be limited to the details shown and described herein, but intend to cover all such changes and modifications as are encompassed by the scope of the present invention.

1 claim:

1. Detonation fuse having a core of high explosive, a sheath surrounding said core, and means for increasing the detonation velocity comprising at least one hollow space arranged within said core, the space extending over the entire length of the fuse and a lining of pliant material being provided against the explosive surroundinathe entire space.

. Detonation fuse according to claim 1, wherein the hollow space is essentially centrally located within said core, and the quantity of the high explosive of said core is at least 12 grams per meter length of the fuse.

3. Detonation fuse according to claim 1, wherein the cross-section of the hollow space is substantially constant over the entire length of the fuse.

4. Detonation fuse according to claim 3, wherein the hollow space is essentially centrally located within said core.

5. Detonation fuse according to claim 3, wherein the cross-section of the hollow space is substantially circular.

6. Detonation fuse according to claim 5, wherein the hollow space is essentially centrally located within said core.

7. Detonation fuse according to claim 1 wherein the pliant material is a thermoplastic synthetic material.

8. Detonation fuse according to claim 7, wherein the thermoplastic synthetic resin is polyolefin.

9. Detonation fuse according to claim 1, wherein the lining is made of a ductile metal.

10. Detonation fuse according to claim 9, wherein the ductile metal is copper.

1 I. Detonation fuse according to claim 1, wherein at least one hose is embedded in the core.

12. Detonation fuse according to claim 11, wherein the hollow space is essentially centrally located within said core.

13. Detonation fuse according to claim 12, wherein the cross-section of the hollow space is substantially constant over the entire length of the fuse.

14. Detonation fuse according to claim 13, wherein the cross-section of the hollow space is substantially circular.

l5. Detonation fuse according to claim 14, wherein the pliant material is a thermoplastic synthetic resin.

16. Detonation fuse according to claim 14, wherein the lining is made of a ductile metal. 

2. Detonation fuse according to claim 1, wherein the hollow space is essentially centrally located within said core, and the quantity of the high explosive of said core is at least 12 grams per meter length of the fuse.
 3. Detonation fuse according to claim 1, wherein the cross-section of the hollow space is substantially constant over the entire length of the fuse.
 4. Detonation fuse according to claim 3, wherein the hollow space is essentially centrally located within said core.
 5. Detonation fuse according to claim 3, wherein the cross-section of the hollow space is substantially circular.
 6. Detonation fuse according to claim 5, wherein the hollow space is essentially centrally located within said core.
 7. Detonation fuse according to claim 1 wherein the pliant material is a thermoplastic synthetic material.
 8. Detonation fuse according to claim 7, wherein the thermoplastic synthetic resin is polyolefin.
 9. Detonation fuse according to claim 1, wherein the lining is made of a ductile metal.
 10. Detonation fuse according to claim 9, wherein the ductile metal is copper.
 11. Detonation fuse according to claim 1, wherein at least one hose is embedded in the core.
 12. Detonation fuse according to claim 11, wherein the hollow space is essentially centrally located within said core.
 13. Detonation fuse according to claim 12, wherein the cross-section of the hollow space is substantially constant over the entire length of the fuse.
 14. Detonation fuse according to claim 13, wherein the cross-section of the hollow space is substantially circular.
 15. Detonation fuse according to claim 14, wherein the pliant material is a thermoplastic synthetic resin.
 16. Detonation fuse according to claim 14, wherein the lining is made of a ductile metal. 